As a wireless communication system becomes more complicated, a linearity of a power amplifier is more critical. The nonlinearity of the power amplifier will affect a total chain adjacent channel leakage ratio (ACLR) of a transmitter, and the 3rd order inter-modulation of the power amplifier is a root cause of the ACLR performance. Therefore, how to effectively lower the 3rd order inter-modulation to increase the linearity of the power amplifier and improve the ACLR performance is an important topic.